Automatic telephone-exchange system.



H. L. FISH.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY I9. |906. nznzwfn Dic. 3I. |911.

whw

Patented July 80, 1918.

3 SHEETS-SHEETI H. L. FISH.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION man MAY19,1905.

REHEWED DEC. 31.1917.

Patented July 30, 1918.

3 SHEETS-SHEET 2 H. I. FISH. AUTOMATIC TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAY I`9, 1906.

RENEWED DECfBI. 1.917.

Patented July 30, 1918.

3 SHEETS-SHEET 3 f narran erariale PATENT ermee.

HERBERT L. FISH, Or BAKERSFIELD, CALIFORNIA, AssIGNOR, BY IJIESNF. ASSIGNMENTS,

. To AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

ATOIVIATIC TELEPHONE-:EXCHANGE SYSTEM.

Applieationv filed May 19, 1906, SeriaLNo. 317,697.

To all whom 'it may concern:

i Be it known that I, I-Imunnrr L. Fisu, a citizen oit' the United States et America, and resident of Bakersfield, Kern county, California,` have invented a'certain new and useful Improvement in vAutomatic` Telephone-Exchange Systems, of which the 'following' is a specification. .My invention relates to telephone systems .in general, bntmore particularly to automatic or semi-automatic telephone exchange systems, and especially to telephone systems in which electric current 'for bothtalking;- and switching purposes is supplied :trom a common. battery or other `(,:entralized source of supply. i

As will hereinafter more 'fully appear, my inventionris in the nature o'li an improvement on the Systems described .in certain copending applications as follows: Serial No. 265,955,1iled June 10, 1905, by IVilson Ii. Campbell, for improvcn'lent in automatic switching and telephone systems; Serial No. 258,508,1ilcd May 2, 1005, by Talbot (fr. Martin, for in'iprovement in automatic common battery telephone systems; Serial No. 312,156, filed April 17, 1900, hy Talbot (r. Martin, for improvement iin telephone exchange systems; and Serial No. 292,011, tiled December' L22, 1905, by Herbert Ii. Fish, ttor improvement in common battery automatic telephone system and apparatus.

Generallystated, the object ot my invcntion the provision of anv in'lproved and highly eti'icient'con'nnon battery. automatic telephone exchange system.

Special objects oit my invention .are the 'provision o't an improved common battery connector; the provision ot' improved means and circuits 'ttor releasing the snf'itches employed 'for establishing' connection between subscribers7 lines; the 1#revision ot improved means tor preventing' a third subscriber :from releasing the switches tempm'arily employed between calling' andI called subscribers; the provision ot improved circuits l'or supplying,- talking;` current to the substations o't` calling'` and called subscribers; the provision oit' imm'ovml means and. circuits ,tor ,ggi'i/'fl'ragg` a calling` subscriber a busy Specification of Letters Patent.

Il atentcd July 30, i191 8.

Renewed December 31, 1917.` Serial No. 209,796.

signal it' the called line is busy; the provision of improved circuits Ylfor operating,` the automatic switching" machinery by which a calling subscriber connects his line with that of the called subscriber; and the provision oil certain details and combinations andfileatures o'tl vimprovement tending,v to increase the general ciliciency and serviceability ot a telephone exchange system ot this particular character. j

To the 'foregoing and other luseful ends, my invention consists in matters hereinafter set forth and claimed.

In the accon'ipanying drawings, vFigure 1 is a diagrammatic representation oit a calling subse1il ei"s lstation X connected with a called snbscribe1"s station #220, said connection being maintained through the medium ot certain central ollice switching' apparatus comprising the Iirst-selector A allotted to the calling` subscribcrs line, and a central battery B :tor providing all necessary current, an improved connector C', and a iirst-selector` A1 allotted to the called suhscriberls line.

. Fig, 2 is a diagrammatic perspective view of the first-selector A.

Fig. 3 is a similar view of the connector C.

It will be understood that the first-selectors A and A1 are substantially the same.

In detail the apparatus .is constructed as follows: rIhe snbscribers station may be of any suitable, known or approved type. Said substation is provided withthe'well-known impiil'se\vlieel 2 which has theiusual vertical impulse-teeth 3 that are adapted to operate the vertical impulse-spring 4lin such manner that the said spring may be pressed intermittently against the greund-post 5 iter the purpose ot sending ground impulses to the vcrtical-line-conductor o't the sub'scribe1"s line. Furthermore, the said limpulse-wheel carries a rotary-impnlse-tooth G which, after the vertical impulses are sent. so acts upon the rotary impulse-finger 7 that a ground impulse is then sent to the rotary side of the subs(.1'il)ers line. The substation is -provided, oi course, with a suitable switch-hool 8. Said switch-hook has a number of cams O, 10 and 11 :tor controlling certain apparatus and circuits of the' substation. The cam-arm 11 controls the so-called lockingcam 12 in such manner that when the switchhook rises, and before the dial (which is not shown) is rotated, the insulating tip 13 upon the end of said locking-cam 12 (that normally rests in the position shown vat substation #220) is'driven'to the inner edge-of the angled section provided at the end of the so-called ground-spring 14, whereby when the dial i's pulled downby the calling subscriber thepin 15 upon the vend Vof `the locking-,dog 161is able toy pass beneath the said locking-cam to raise the said c am a trifle farther and thereby cause theV said insulating tip 13 to fall behind the said angled section of the ground-spring 14, permitting said spring, therefore, to make electric contact with a ground-spring 17. The Y engagement of said ground-springs 14`and 17, upon the yoperation described, places the ground-post 5in connection with the substation ground, whereby when the subscriber releases the dial after pulling itdown as de-, scribed, the vertical impulse-teeth 3 will then act first upon the vertical impulse-linger 4, and after that the rotaryY impulse-tooth 6 acts upon the rotary impulse-linger 7, as previously stated. The subscriber is, of course, provided `witha transmitter 18 and Van induction-coil 19, the primary Winding 2O of which is connected (when the switch-hook i's raised) in series with the transmitter 18 and i across the subscribers line; and the secondary winding 21 is iconnected in a local closed circuit in series with the Vreceiver 22. Furthermore, the substation lis provided with a ringerv23 that is normally bridged across the subscribers line, when the switch-hook is down, in series with a condenser 24.

lWhen the switch-'hook is'down the cam-arm tained lacross the line; but the `spring 25v being depressed, two other springs 27 and k28 are keptnormally separated, which, when the switch-hook rises, are normally closed while the said springs 2,5 ,and 26 spring apart. It .will be noticed thatthe said springs 27 and '28 control the Vconnection between the two conductors of the subscribers line through the aforesaid transmitter 18, and through the l primary winding 20 of the induction-coil 19. Even after the switch-hook L switching apparatus, after 'said apparatus is once disturbed, comprises three releasesprings 30, 31 and 32 so controlled by the rcam-arm 9 that when the switch-hook debanks 42 and 43, respectively; Being-raised,

the shaft is rotated by the rotary-magnet 44. The release-magnet 45 is employed for restoring the switch after it has been operated. The vertical and rotary line-relays 46 and 47, the line-switching-relay 48, back-releaserelay 49, and private-magnet 50 are for controlling said vertical, rotary and release magnets. The switch-shaft has, in addition to the details already described, the usual cam 51, the longitudinal teeth 52 for rotating the switch, and the circular teeth 53 for raising it. Associated with said circular teeth is the channel 54 normally occupied by the. shaft-rest 55.

The switch-shaft is maintained in normal position by the normalpost 56 and the normal-post-arm'57, against which post the said arm 57 is retained by the spring 58. Y

The connector C is also ofv a well-known type, and is structurally similar to the selec# tor, but the circuits are quite different. Said connector like the selector isprovided with a switch-shaft 59 and wipers 60, 61 and 62, to which latter are allotted the line and private banks 63 and 64, respectively. There is also the shaft-cam 65, the longitudinal teeth 66,

the circular teeth 67 ,theshaft-rest 68, normal-post 69, norinal-postearm 70 and the coil-spring 71. Furthermore, the switch is provided with the usual vertical-magnet 72, the rotary-magnet 73 and the release-magnet 74. In addition, the connector has a number of' auxiliary relays as follows: The

vertical-line-relay 75 which is provided withk two windings 76 and '77, the rota'ry-line-re-V lay 78 which is also provided vwith two windings 79 and 80, theprivate-magnet 81, the back-bridge-relay 82 withtwo windings 83 and 84, the busy-lock-out-relay 85, the release-relay 86, and the ringer-relay'87. The said relays control circuits which will here-v inafter be set forth.

The operations by which the subscriber at the calling station X establishes connection with the called subscriber #220 are as follows: He (the calling subscriber) removes his receiver from the switch-hook and then proceeds to operate the dial twice for the digits 2 and once for the digit O. As soon as the dial is drawn down for the first digit 2 connection is established from the ground terminal vGr of battery B to the ground-post 5by way of the ground-springs 14 and 17, when said springs come into contact in the manner described.` .As the impulse-wheel 2 returns to normal position, the vertical impulse-finger 4 is pressed against the said ground-post 5 twice in succession, thereby twice energizing the vertical-line-rclay 46 of the first-selector Al.' Each time that the said relay is energized the circuit is closed from ground (il through the ground-springs 14 and 17 to the grouml-post 5, thence to the vertical impulse-spring 4, vcrtical-line-eon ductor S8, line-switching-relay springs 89 and 90, conductor 91, vertieal-line-1elay 46 to the battery-lead 92, and through battery B to ground G. Vhen the vertical-line-relay is energized the line-relay spring 93 is pressed onto the ground-spring 94-and a circuit is established each time through the vertical-magnet 41 :tor energizing said vertical-magnet. The current through the said vertical-1nagnet passes in its course from ground G3 through the said springs 94 and 93 to, the 'conductor 95, thence through the Vertical-magnet 41 to the battery-lead 92, thence through battery B to ground G; Each time that the vertical-magnet 41 is energized it attracts the vertical-armature 96, which latter, through the medium of the vertical-arm 97, causes the vertical-pawl 98 to engage the circular teeth 53 and thereby raise the switch-shaft 37. It will be understood that at the first operation of the vertical-arm 97 the L-shaped piece 99 upon the under side oit said vertical-arm lifts the release-link 100 from the lug 101 of the doubledogy 102, whereby the said double-dog is caused to rotate so that the vertical and rotary dogs 103 and 104 are drawn against the circular and longitudinal teeth 53 and 52, respectively. Said verticali-dog 103 operates to hold 'the shaft at each vertical step in order that it may be raised in a well-known manner. lWhen the shaft is raised two steps for reasons` stated, the line and private wipers 38, 39 and 40 are raised to the second level oit' the banks 42 and 43, respectively, retaining the line-wipers opposite the irst contact oil the second level of the said linebank 42, and the private-wiper 40 opposite the first contact ot the second level oit- `the pri vateban k 43, ready to be rotated into engagement with the contacts ol said banks. The shatt being` thus raised, and when the lug 6 et' the impulse-wheel 2 engages and presses the rotary i1npulsefinger 7 against the ground-post 5, the rotary-line-relay 47 is then energized in turn. The circuit over which the energizing current passes may be traced from ground G1 to the ground-post 5, thence to the rotary impulse-finger 7, rotaryline-comluctor 105, line-switching-relay springs 106 and 107, conductor 108, verticallinerelay 46 to the batterydead 92, thence through battery B to ground G. Vhen the said rotary-line-relay 47 becomes magnetized the spring 109 is pressed onto the i-roundspring 94, and as a result the private-mag-` net 50 is also energized. The path o1 the current may be traced from ground G through the springs 94 and 109 to the conductor 110, thence to the private-1nagnet 50 and batterydead 92, and through battery B to ground G. As soon as the private-mag net 50 attracts its armature 111 the privatesprings 11.2 and 113 that are normally open close into contact, the springs 113 and 114 that are normally engaged are forced apart, and the springs 114 and 115 are closed into contact. At the instant that the springs 112 and 113 come into contact the rotary-magnet 4.4 is energized through the following eircuit: from ground G through the springs 116 and 117 on the release-armature 233 to the conductors 119 and 120, privatosprings 113 and 112 tothe interruptcr-springs .121 and 122, thence through the rota1'y-magnet 44 to the battery-lead 92 and through battery B to ground G. When the rotary-magnet 44 is magnetized it attracts its armature 123, whereby a number o't' operations are pern formed sinniltaneously. The rotary-pawl 124. is thrust into engagement with the first one of the longitudinal teeth 52 so that the shaft 37 is rotated one step. It should be stated that as soon `as the switch-shaft 37 is raised the first step the switch-shaft,springs 125 and 126 close into contact, the Jformer ot' said springs being connected to ground G". As soon as the switchfshait 37 is rotated, described, the springs 127 and 12S controlled by the cam 51 separate and the spring 12S engages instead the spring 129. The object in maintaining the springs 127 and 12S normally closed` as described, is to provide a, means whereby a lamp signal 130 is lighted whenever the switch-shai"t 37 is raised, and whereby the said lamp signal will remain lighted as long as the switch-shaft 37 is raised but not rotated. The circuit lor energizing said lamp 130 may be traced from ground G through the switch-shaft off-normal springs 125 and 126, conductor 231 to the spring 12S, thence through the spring 1,27, conductor 132 to the lamp 130, thence through battery B to ground G. 1n this way the switch attendant is always notified 'it a selector is oill normal. As soon as the springs 127"and 128 come into Contact, after the shaft 37 is rotated` the line-switching-rew lay 4S is short-circaited over the -following circuit: from ground G4 to the olli-normal springs 125 and 126, conductor 231 to the cam-spring 12S, thence to the spring 129, conductor 133 and line-switching-relay 48 to the conductor 1,34. thence through the private-springs 112 and 113 and conductor 120, release armature springs 117 and 116 to ground G3. Assuming that the first nine trunks leading from the second level of the line-bank 42 are busy the first ynine contacts of the second level of the private-bank 43 will be connected to ground. Therefore, at the first step of the shaft 37 the privatewiper engages a grounded contact. As the rotary-armature 123 strikes the rotarymagnet 44 the interrupter-finger 135l separates the interrupter-springs 121 and 122 and destroys the energizing circuit through the said rotary-magnet. By the time that this occurs the `original energizing circuit for the private-magnet has also been destroyed, since the, rotary-line-relay 47 is energized only by a momentary impulse from the-calling subscribers station. But the rotary-armature-finger 136 prevents the private-armature v11.1 from regaining its normal position before the rotary-magnet 44 has completed its work. In the meantime, since the private-wiper .40 `finds the first contact of the second level of the private-bank- 43 grounded, a new energizing circuit is provided through the private-magnet 50. The current in this energizing circuit' flows from ground G of the battery B and through whatever switch is occupying the first trunk, and through the bank-multipling conductors to the said ground private-contact,

, thence by way of the private-wiper 40, conductor 137, back-release-relay 49, conductor 138, private-springs 114 and 115 to the private-magnet 50, thence to the battery-lead 92 and through battery B to ground G. This circuit having once been established, it is then maintained as long as the private-wiper 40 is rotated into engagement with grounded private-contacts. Therefore, the original energizing circuit through the rotary-magnet 44 is not destroyed until after the said private-magnet is denergized, as will be described. Therefore, when the interrupter-finger 135 destroys ,the energizing circuit through the rotary-magnet 44, as soon as the rotary-armature returns tonormal position, the energizing circuit through the rotary-magnet is again Iestablished in order that the shaft 37 may be advanced another step., These operations continue until the private-wiper finds a non-grounded contact. The assumption be-I ing that only thev tenth trunk is idle the wipers will be rotated into engagement with the tenth trunk. The vertical-wiper y38, therefore, will engage the vertical-trunkconductor 139 vand the rotary-wiper39 will engage the rotary-trunk-conductor 140. At the same time the private-wiper 40 will. establish connection with a trunk-release-conductor 141. The energizing circuit through the private-magnet 50 is thus destroyed so that thef private-armature 111 is restored afterV the last operation of the rotary-armature 123. Thfeprivate-springs 112 and i 113 will, ofcourse, be again separatedso that the short-circuit across the line-switching-relayA 48 is removed, andthe said relay then instantly energized over the following circuit; from ground G4 over the circuit as .previously traced to the said line-switching- :relay 48, thence over the conductor 134 and -through the interrupter-springs 121. and 122 and through the rotary-magnet 44 to the battery-lead 92 and from battery B to ground G. `In this circuit the current that fiows is too small to magnetize the rotary-magnet 44 since the said line-switching relay 48 is of a very high resistance. For the same reason the back-bridge-'relay 49 is not energized through the circuit previously described in series with the private-magnet 50. As soon as the line-switching-relay 48 pulls up, as just described, the line-switching-relay springs 89 and 106 are separated from the line-switching-relay springs 90 and 107 vand pressed instead into contact with the springs 142 Vand 143.' As a result the verticaland rotary line-relays 46 and 47 are cut off from the subscribers line-conductors 88 and 105 and the said conductors are put in connection with the trunk-conductors 139 and 140, respectively, as followsyfrom the conductor 88 through the line-switching-relay ysprings 89 and 142, conductor 144, vertical-wiper 38v to the vertical-trunk-conductor 139, the rotary-line-conductor 105 to the line-switching-relay springs 106and 143, conductor 145 and rotary-line-.wiper 39 to the rotary-trunkconductor 140. The subscribers station is, therefore, put in connection with the Connector C, as shown in Fig. 1. The subscriber upon operating `his dial for the second digit grounds the vertical-line-conductor 88 first twice, and asa resultthe vertical-line-relay 75 is energized over the following circuit: from ground G1 to the ground-post 5, thence over the vertical impulse-finger 4 to the vertical-line-conductor 88, line-switching-relay springs 89 and 142, conductor 144, verticalline-wiper 38, vertical-trunk-conductor 139, vertical line relay winding 77, conductor 146, back-bridge-relay springs 147, 148 and 149 to the battery-lead 92 and through battery B to ground G; When the said relay 75 is energized the spring 150 is pressed onto the ground-spring 151, and as a result the vertical-magnet 72 is energized by a flow of current from ground G5, through the said springs 151 and 150, conductor 152, privatesprings 153 and 154, conductor 155, sideswitch-wiper 156, contact-point 157, verticalmagnet 72 tok the battery-lead 92, and through battery B to ground G. The said vertical-magnet then attracts the vertical-armature 158 and through the medium of the vertical-arm 159 causes the vertical-pawl 160 to yengage the circular teeth 67, raising the shaft 59 two steps. The shaft being thus raised, the line-wipers 60 and 61 and the private-wiper 62 are raised to the second level opposite the first contact of the second level of the line and private banks 63 and 611, respectively, in readiness to be rotated into engagement with the contacts of said banks. Vhen the rotary-lineconductor 105 is grounded, the rotary-line-relay 78 of the connector C is energized in turn, and the current that passes through said relay flows over the following circuit; from ground G'l to the ground-post 5, thence over the rotary impulse-finger 7 to the rotary-line-conductor 105, thence to the line-switching-relay springs 106 and 118 of the first-selector A to the conductor 115, rotary-line-wiper 39, rotary-trunk-conductor 1410, winding 80 of the rotary-line-relay 78, conductor 161, backbridge-relay springs 118 and 119 to the battery-lead 92, and through battery B to ground G. Then the said rotary-line-relay becomes magnetized, the spring 162 is pressed onto the ground-spring 151, and as a result the private-magnet 81 is magnetized. The current through the said private-magnet may be traced from ground G5 to the springs 151 and 162, private-magnet 81, conductor 168, back-bridge-relay springs 117, 118 and 119 to the battery-lead 92, and through battery B to ground G. Vhen the private-magnet attracts its armature 161 the escapement-tinger 165 of the side-switch D clears the eseapen'ient-tooth 166, and when the armature returns to normal position the retracting-spring 167 draws the side-switch into second position, with the said escapeinent-tinger 165 resting between the teeth 166 and 168. After the side-switch D has passed to second position the, subscriber operates his dial for the last digit of the number 220, and as a result the verticalline-conductor 88 is grounded ten times. The vertical-line-relay 75 is again energized over the same circuit ten times, but instead of the vertical-magnet 72 being operated as a result the rotary-magnet 7 8 is energized. The change is due to the passage of the sideswitch-wiper 156 onto the contact-point 169 after having left the contact-point 157. r1`he rotary-magnet 7 8 is therefore energized ten times, the current flowing from ground G5 to the side-switch-Wiper 156, as in the previous case, but thence it passes onto the contact-point 169, through the rotary-magnet 78 to the battery-lead 92, and through battery B to ground G. The rotary-armature 170 is attracted ten times, so that the rotarypawl 171*l by engaging the longitudinal teeth 66 rotates the shaft 59 ten steps, carrying the line-Wipers 60 and 61 into engagement with the vertical and rotary normal-condiictors 171 and 172, respectively, and the privatewiper 62 into engagement with the privatenorrnal-conductor 178. As soon as the rotary-line-conductor 105 is grounded for the lasttime the rotary-line-relay 78 is again energized once so that the private-magnet 81 is energized in turn once more. 'lhe sideswitch D, as soon as the eseapement-finger 165 clears the escapement-teeth 168 and 1711, :is drawn into third position bv the retracting-spring 167. The side-switch-wipers 175, 17 6, 177 and 17 8 then pass into engagement with the contact-1mints 179, 180, 181 and 182. When the side-switch-wipers 177 and 178 engage the contact-points 181 and 182 the subscribers extended line-coluluctors 139 and 1-10 are placed in connection with the normai-conductors 171 and 172, respectively. The circuits are as follows: from the conductor 139, through the condenser 183, conductor 181, ringer-relay springs 185 and 186, side-switch-wiper 177, contact-point 181, conductor 187, vertical-line-wiper 60 to the if'ertical-nornnil-conductor 171, then from the rotary-trunk-conductor 14:0 through the Condenser 188, conductor 189, ringer-relay springs 190 and 191, side-switch-wiper 17 8, contact-point 182. conductor 192 to the rotary-line-Wiper 61, thence to the rotarynormal-conductor 172. As soon as the sideswitch-wiper 176 engages the grounded contact-point 180 a guarding potential is established at the private-wiper 62, whereby no other subscriber may be able to call in upon the seized line. The circuit over which said potential is established is as follows; from ground G6 to the contact-point 180, thence to the side-switch-wiper 176, conductor 193 and private-wiper to the tenth contact of the second level of the private-bank 6-1. Not only is the said guarding potential established but an energizing current is sent through the ringer-relay 87 from the ground G7 through a circuit interruptor F, conductor 1,9-1 to the contact-point 179, thence through the side-switcli-wiper 175, conductor 195, ringer-relay 87, conductor 196,

springs 147, 1118 and 119 to the battery-lead 92, and through battery B to ground G. Each time that a circuit is closed through the circuit-interrupter l? the ringer-relay 87 pullsl up and bridges the ringer-generator 197 across the normal-conductors 171 and 172 that lead to the called subscribe1"s station. The circuit may be traced from the ringer-genera tor 197, through the ringer relay springs 198 and 186,- side-switch-wiper 177, vertical-linewiper 60, vertical-normalconductor 171, verticaldine-conductor 199, condenser 201, ringer 200 to the rotary-linecoiuluctor 202, thence to the rotary-normalconductor 172, rotary-line-wiper 61, contactpoint 182, side-switch-wiper 17S, ringer-relay-springs 191 and 203` back to the ringergenerator 197. Then the subscriber at the substation #220 responds he removes his receiver 2041 from the switch-hook 205 and thereby closes connection across the telephone line-conductors 199 and 202. An energizing circuit is, therefore, closed through the back-bridge-relay 82. The current may be traced from ground G8 through'the winding 84, through the conductor 206, conductor 189, ringer-relay-springs 4190 and 191, side-switch-wiper 178, contact-point 182, rotary-line-wiper 61, conductor 17 2, rotaryline-conductor 202, primary winding 207 of the induction-coil 208, trans1nitter'209 to the vertical-line-conductor 199,`thence vto the vertical-normal-conductor 171, wiper 60, contact-point 181, side-switch-wiper 17 7 ringerrelay-springs 186 and 185, conductor 184 to the winding 83 of the coil 82, thence to the battery-lead 92, and through battery B to ground G. It should be noticed that the release-relay 86 is normally short-circuited as follows: from the said relay 86to the conductor 210, springs 148 and 149 of the relay 82, conductor 211 and conductor 212 back to the said relay 86. ,'However, as soon as the back-bridge-relay 82 pulls up, the said short-circuit is removed when the springs 148 and 149 are separated by the relay v82. Then the said relay 82 becomes magnetized as stated, not only is the short-circuit removed from the relay 86 but the spring 147 is shifted from normal connection with the battery-lead 92 l into connection with the spring 213 and, therefore, with ground G9. As soon as the springs 147 and 213 come into contact the ringer-relay 87 is short-circuited so that it will be impossible for said relay to be further energized. The short-circuit extends from ground GJ through the springs 21,3 and 147,`conductor 196, ringer-relay 87, side-switch-wiper 175, contact-point 179, conductor 194, interrupter F to ground G7. Furthermore, talking battery current is established on the line of the calling subscriber over the following circuit: from the same ground G9 and through the springs 213 and 147, conductor 146, winding 77 ofthey Vvertical-line-relay 75, vertical-trunk-conductor 139, first-selector-wiper 38, lineswitching-relay-springs 142 and 89, verticalline-conductor 88, transmitter 18, primary winding 20 of the induction-coil 19, rotaryline-conductor 105, line-switching-relaysprings 106 `and 143, wiper 39, rotarytrunk-conductor 140, winding 80 of the rotary-line-rela'y 78, conductor 210, releaserelay 86 to the battery-lead 92, and through battery B to ground G. In this circuit not only is the transmitter of the calling subscriber provided with battery current, vbut the vertical, rotary and release relays 75, 78 and 86, respectively, are also energized. -gize 'or pull up the trunk-release-springs 214 and 215 are pressed into Contact, and when the release-relay 86 is energized the springs 216 and 217 are separated. It will be noticed that the release-magnet 74 is in a circuit that Vcomprises the said springs 216 and 217 and the springs 214 and 215, and that the trunk-release-conductor 141 v that leads to the first-selector A is connected to When the said line-relays ener-V ground G3, as previously described, and at any time thesaid springs i214'and 215 are closed into contact,simultaneously with the springs 216 and 217, the said release-magnet 74 will be energized. The energizing circuit would be from the said ground G3 at the rst-selector, thence through the releasearmature-springs 116 and 117, conductor 119private-springs 113 and 114, conductor 138, back-release-relay 49, conductor 137, private-wiper 40, trunk-release-conductor 141, trunk-relase-springs 214 and 215, `springs 216 and 217 to the release-magnet 74, thence to the battery-lead 92 and through battery B to ground Therefore, since while the subscribers are talking the line-relays 75 and 78 are energized, as described, it is necessary to have the said release-circuit open at some point, which point appears between the said release-relay-springs` 216 and 217. After the subscribers have established connection with each other they may converse over the following circuit: from the transmitter 209 to the primary winding 207 of the induction-coil 208, rotary-line-conductor 202, rotary-normal-conductor 172, wiper 61, contact-point 182, side-switch-wiper 178, ringer-relay-springs 191 and 190, condenser 18,8, rotary-trunk-conductor 140, wiper 39, line-switching-relay-springs 143 and 106, rotary-line-conductor 105, primary winding 20 of the induction-coil 19, transmitter 18, v'ertical-line-conductor 88, line-switching-relay-springs 89 and 142, wiper 38, verticaltrunk-conoluctor 139, condenser 183, ringerrelay-springs 185 and 186, side-switch-wiper 177, contact-point 181, wiper 60, verticalnormal-conductor 171, vertical-line-conductor 199 back to the transmitter 209. The said primary windings 207 and 2,0, respectively, being provided with their allotted secondary windings 218 and 21 (the said secondary windings being connected in series with the receivers 204 and 22, respectively),

'the conversation may then be carried on between the subscribers in a well-known inanner. The guarding potential previously described for the private-wiper 62 not only protects the called line from further seizure, but causes an energizing circuit to be established, through the bridge-cut-off-relay 219 of the called first-selector A1. The circuit may be traced from ground G6 through the side-switch-wiper 176 to the private-wiper 62, thence over the private-normal-conductor 173, line-switching-relay 219, rotary-magnet 220 to the battery B and to ground G. The object in energizing said line-switching-re- -lay is to disconnect the line-relays 221 and 22.2 from across the talking line, for reasons well A known. After the subscribers are through talking either subscriber, by hanging up his receiver, may restore the switches by simply opening up his line. It will be noticed that as soonas the talking current is established on the line of the calling sub- Scriber, and as soon as the trunlereleasesprings 214 and 215 come in contact, a flow of current is established through the windings 76 and 79 of the line-relays 75 and 78 in series. The flow of current will be from ground G3, as previously described, and over the same circuit to the trunk-rel fasespring 215, thence through the windings 79 and 76 to the battcry-lead 92, and through battery B to ground Gr. Therefore, if the calling subscriber hangs up his receiver 1irst#and although he will destroy the energizing circuit previously described that includes his transmitter and the windings 77 and 80 of the line-relays 75 and 7S and the release-relay 8th-the line-relays 7 and 78 will not be denergized because of the circuit established through the windings 76 and 79; but the rebase-relay 86 will be deenergized and the only open contact in the release-circuit that has been described is closed as soon as the springs 216 and 217 come into contact. As a result the release-magnet 74 in series with the backrelease-relay 49 of the first-selector A will be energized. The release-ammi ture 225 will be attracted, the double-dog 226 will then be struck by the said releasesarurature, and the lug 227 will then be engaged by the aperture on the end of the release-link 228. The shaft 59 will be deprived ot' its locking-dog 229 and the coil-spring 71 will rotate the said shaft to normal rotary position until the shaft-rest 68 finds the aperture 230, at which time the shaft will fall to normal vertical position. The back-release-relay 49 of the .first-selector A being energized the springs 223 and 224 are pressed into contact andan energizing circuit is, therefore, established through the release-magnet 45 of the said selector A. The current through the said magnet 45 Hows from ground Gr'L through the switch-shaft-springs 125 and 126, conductors 231 and 232, back-releaserelay-springs 224 and 223 to the releasemagnet 45, thence to the battery-lead 92 and through battery B-to ground Upon be coming energized the release-magnet 45 attracts theV release-armature 233, thrusting the releas`e-link 100 over the lug 101. As soon as the said release-armature 233 is attracted the springs 116 and 117 are pulled apart so that the energizing circuit comprising the back-release-relay 49 and release 1nagnet'74 of the connector is broken, and at the same time d the energizing circuit through the windings 76 and 79 of the vertical and rotary line-relays 75 and 78, respectively, is also destroyed. Evidently the line-relays 75 and 78 and the release-n'iagnet 74 of the connector will regain their normal conditions. The back-release-relay 49. of the selector A is also energized, for the reasons stated, and when denergized the circuit through the release-magnet 45 is also broken, which latter then permits the re- .lease-arn'iature 233 to be drawn into normal place by the spring 117, or by any other suitable spring. The release-armature 233, upon returning, withdraws the locking-dog 104 from the circular teeth 52, permittingthe s\\'itclisl1aft 37 to be rotated to normal rotary position by the spring 58, at which time the shaft-rest finds the slot 54, and the shaft 37 then drops to normal vertical position, separating the ott-normal springs and 126 and the cam-springs 128 and 1.29. The line-switching-relay 48 is then restored and as a result the vertical and rotary line-relays 1-6 and 47 are brought back into connection with their respective line-conductors 88 and 105. 1f the called subcriber restores his receiver before the calling subscriber he will break the circuit that encrgizcs the back-bridge-relay 82. Said relay upon de'e'nergizing will permit the springs 147, 148 and 149 te pass into contact and thereby short-circuit the rebase-relay 86. 1 `urthermore, the spring 147 leaves the spring 213, and the circuit for providing the calling subscriber with talking battery current is thereby cut ott'. Although thesaid talking current is cut ollI from the slibscribers line, and although as a result the windings 77 and 80 ol the relays 75 and 78 are deprived of current, the said line-relays 75 and 78 are energized because of the circuit that is maintained through the windings 76 and 79 and over the trunk-1elcase conductor 141, as previously described. '.l`herefore, the trilnk-release-spriugs 214 and 215 are retained together even after the baclebridge-relay 82 denergizes. However, as soon as the release-relay 86 permits the springs 216 and 217 to come into contact the release circuit through the release-magnet 74 and the back-relcase-relay 49 is again closed with the result already described. 1f the line of the called subscriber #220 is busy at the time that a. subscriber calls there will be a guarding potential at the tenth contact ol the second level of the private-bank 64, which contact corresponds to the line of the said subscriber #220. The line may be busy either fron'i being called or from calling. 1f the subscriber #220 is calling the guarding potential will be established when the switch-shaft 234 rises and permits the springs 235 and 236 to come into contact. The circuit over which the guarding potential is established is as follows: from ground G10 through the springs 235 and 236 to the trunk-relcase-conductor 173 and to the said contact-point. 1f the subscriber has been called there will be another connector set on the line of the subscriber #220 and a guarding potential will be established from the ground terminal similar to the ground terminal G, through a side-switchwiper similar to the side-switch-wiper 176, and through a'private-wiper 62 to the said contact. 1f the tenth contact ofthe second level of the private-bank 64 is grounded at thel instant that the private-wiper 62V is rotated Vontothe said contact an energizing circuit is closed through the ringer-relay 87 from ground G of battery'B tothe said contact, thence to the private-wiper 62 through the side-switch-wiper 176, contact-point 237 to the side-switch-wiper 175, thence over the conductor 195 to the ringer-relay 87, vconductor 196, baok-bridge-relay-springs 147, 148 and 149 to the battery-lead 92 and through battery B to ground G. As soon as the ringer-relay 87 pulls upr the springs 238 and 239 are pressed into contact. Furthermore, as soon as the calling subscriber grounds the rotary-line-conductor 105 for thelast time, the rotary-line-relay 78 is energized over the usual circuit, and when the springs 151 and 162 are pressed together the private-magnet 81 is also energized. VAt the same time that the private-magnet 81 is energized the busy lock-out relay 85 is also energized from ground G5 through vthe springs 151 and 162, conductor l240, springs 238 and 239, conductor 241 to the relay '85 thence through the switch-shaft-springs 242 and 243 (which are incontact) to the battery-lead 92 and through battery Bl to ground G. VAs soon as the relay 85 is energized the springs 244, 245 and 246 close and at the same time the private-magnet closes the springs 247 and 248. As a result the energizing circuit for the private-magnet 81 is shifted from ground G5 to ground G11 as follows: from ground G11 through the springs 246 and 245, conductor 249, privatesprings 248 and 247 to the private-magnet 81 and conductor 163, springs 147-, 148 and 149 to the battery-lead 92 and through battery B to ground G. Also the energizing circuit for the busy lock-out relay 85 'is shifted from ground G5 to ground G11, the new circuit being as follows: from ground G11 through the springs 246, 245 and 24T/1 through the said coil 85, switch-shaftsprings 242 and 243 to the battery-lead92, and from battery B to ground G. As a result the private-magnet 81 and the relay 85 will be locked, so to speak, over energize ing circuits controlled by relays 81 and 85, as described. Therefore, when the rotaryline-relay 78 denergizes and the spring A162 leaves the spring 151 the separation will produce no effect upon the private and busy lock-out magnets 81 and 85. Not only does the busy lock-out relay 85 control the springs 244, 245 and 246, but the springsv 250 and 251 are also pressed into contact and a busy signaling circuit thereby' established through the'receiver of the calling subscriberf The busy current may be generated, in a suitable coil 252, for instance (Fig. 1), which current will then iow from the said coil to the conductor'253, thence through the springs 251 and 250 and through the condenser 183 to the vertical-trunk-conductorr 139, verticalline-wiper 38 of the selector A, conductor 144, line-switching-relay-springs 142 and 89, vertical-lineconductor 88, through the transmitter 18 and primary winding 20 of the induction-coil 19 to the rotary-line-conductor 105, thence to the line-switchingrelay-springs 106 and 143 of the selector A, conductor 145, rotary-line-wiper 39 and rotary-trunk-conductor 140 to the winding 80 of the rotary-line-relay 78, thence by way'of the conductor 161 and through the springs 148 and 149 to the battery-lead 92, and through battery B toground G.- The current passing through the winding 20 of the induction-coil 19 at the substation X induces a current into the secondary winding 21, which coil being in serieswith the receiver 22 sends the current through the said receiver. The subscriber upon hearing the busy-signal will understand that the line is busy and will restore his receiver, whereby the switch-hook cam-arm 9 Vforces the release-springs 30, 31 and 32 vinto' contact, grounding the vertical and rotary line-conductors 88 and 105 simultaneously. The ground connection to the vertical-line-conductor 88 is from ground G1 through the ground-springs 14 and 17 to the releasespring 30, thence to the spring 31 and to the said conductor 88. To the rotary-line-conductor 105 the connection is from ground G1 to the release-spring 30, thence through the springs 31 and 32 to the rotary-line-conductor 105. Grounding the vertical and rotary line-conductors 88 and 105 simultaneously sends a flow Lof current through the windings 77 and 80 of the vertical and rotary line-relays 75 and 78 of the connector() over circuits that are already known. The said relays 75 and 78 will, of course, be energized so that the trunk-release-springs 214 and 215 will be brought together, establishing a circuit (previously described) through the release-magnet 74 from ground G3 at the first-selector A, through the springs 116 and 117, private-springs 113 and 114 to the b'ack-release-relay 49, thence to the private-` wiper 40, trunk-release-conductor 141to the trunk-release-springs 214Y 'and 215, thence through lthe release-relay-springs 216 and 217 to the release-magnet 74, thence through said magnetto battery-'lead 92' and through battery B to ground G. -From the trunkrelease-spring215 a flow of current is also established through the windings 79 and 76 of the relays 75 Vand 78 over circuits that have been previously described. The release-magnet 74 of the connector',`being magnetized, will release the switch-shaft 5 9 and side-switch D, as already described, and the back-release-relay l0 will pull up and energize the release-magnet -15 of the selector A. The switch-shaft 50 in falling to its lowest; position, through the medium ot' the nor- 1nalpost-ar1n 70, separates the switch-shal'tsprings 2f'l2 and 2113. Said springs being included in the energizing circuit through the busy lock-out relay 85, the said relay will then deenergizc, at which time the springs 211, 245 and 2116 will separate to deenergize in turn, as a result, the private- 1naguct 8l. As soon as the release-armature ot' the release-magnet t5 pulls up, the release-circuit through the lastnamet1l windings 76 and 79 will be broken, producing no effect; but when the subscriber-s switch-hook descends far enough t0 permit the releasesprings 80, 31 and 32 to separate au energizing circuit tl'nough the windings 77 and 80 ot' the line-relays 75 and 78 will also be destroyed, and the trunk-releasesprings 211 and 215 separated as a result. The release-magnet 71 and lnicli-release-relay 41S) will be deenergized, restoring the connector and the selector' in a manner that is well known.

The resistanccs oil? the relays and magnets of the connector' may be varied to any suitable degree, but good results are obtained when the Vertical-magnet 72, rotary-magnet 73 and release-magnet 711 are wound to (30 ohms; the windings 70 and 70 o'l the linerelays 75 and 78 to 350 and 250 ohms, respectively; the windings 77 and 80 o'l" the said relays 75 and T8 to 500 ohms each; the busy lock-out relay 85 to 350 ohms; the private-magnet 81 to 350 ohms; the release-relay 80 to 100 ohms; the windings 88 and 811 of the backbridge-relay 82 to 350 ohms each; and the ringer-relay 87 to 500 ohms. It will be evident, when a connector is locked on a busy line, that since the side-switchwipers 177 and 178 are not in connection with the contact-points 181 and 182 the calling subscriber cannot hear any conversation that may be going on between the subscriber #220 and any other subscriber and, in tact, he cannot interfere with the subscriber :#:220 at all.

In an automatic system a number olf substations, like the substations X and #220, are often bridged across the same line, and it' when two subscribers are couununicating (for instance as when the subscriber' X is communicating with the subscriber #220) one of the other subscribers on the same line with the subscriber X should take ofi his receiver and begin to voperate his dial he would ground the vertical and rotary line-conductors 88 and 105 through the transmitter 18 and primary winding 20 of the substation X. Ordinarily, in automatic telephone systems of the class herein described, il" both li11e-conduet'ors 88 and 105 are grounded .simultaneously, the switching,` apparatus is released; but in my improved system such grounding ol: the line-conductors will not produce such undesirable results. (irollnding the rotary-line-conductor 105, whileI the subscribers are talking, has no etl'cct upon the release-relay 8G, and it is only by operating` the said relay that the subscribers on the line leading to the substation X can release the switches. The rclease-relay 80 will remain energized when the rotary-line-conductor 105 is grounded .over the Following circuit: from ground to the said rotary-line conductor, thence through the winding 80 o'lE the rotary-linerelay 78, conductor 210 to the said releaserelay 86,thenceto battery B. Grounding the vertieal-line-couductor 88 simply cuts the flow of current through the winding 77 o'li the vertical-line-relay 75. which produces no result of significance. ln a similar way. il. a subscriber on the line leading to the substation #220 should ground both line-conductors 100 and 202, the l)ack-bridgerelay 82 would remain energized, having one ot its windings (namely the winding 8l) shortcircuited; but the other winding 83 would still receive current from the vertical-lincconductor 199. r1`hc subscribers upon the called line can only release the switches by operating tirst'I the lnucl-release-relay 82, and since this cannot be done by grounding the line-cfmduetors the switches will not be released.

The selectors herein relerred to may be of the gelleral type disclosed in Patent No. 815.321. issued March 13. 1900. The connectors referred to may be o'l the general type disclosed in Patent No. 815.170, issued March 13. 1900.

From the foregoing it will be seen that l provide an improved automatic telephone exchange system in which the connection between ealling and called subscribers lines cannot be released by accidental grounds on the lines. ln other words. it is the opening ol a subscribel"s telephone line which accomplishes the release, and this may be done by either the calling subscriber or the called subscriber. and a ground on either line will not produce a premature release ol Ithe talking purposes is supplied through imestablished connection. (iurrent for proved circuits and apparatus to the substations oi calling and called subscribers when any two substations are connected together. The line-relays ol the connectors have line and local circuits. and current is furnished through both the local and the line circuits 'from the single common battery, as explained.

I do not. however, limit myself to the exact construction shown and described, as

various modifications for obtaining the toregoing and other useful ends will be obvious to those 'skilled in the art.

What I claim as my invention is 1. In a telephone 'exchangersystenn the combination of a calling telephone line, a called telephone line, automatic sn'iitching machinery for connecting the two lines, means for grounding a telephone line to release the switching machineryA before the called subscriber answers, and means for opening a telephone, line circuit to release the switching machinery atter the called subscriber answers;V

2.*In a telephone exchange system, the combination of a calling Ytelephone line, a called telephone line, automatic switching machinery for connecting the two linesgtogether,l means for grounding the calling liuc to release the switching machinery before the called subscriber answers, and means tor opening` the circuit of either telephone line to release the switching machinery after the called subscriber answers.

3; In a telephone `exchange system, thc combination of a' calling telephone line, a called telephonev line, automatic switching machinery for connecting the two lines to'-v gether, means :tor grounding a telepiione line to release the switching machinery before .the called subscriber answers, and means tor opening" up the circuit of either telephone line tol release the switching machinery attel1 the called subscriber answers.

4. In a telephone exchange system, the' combination of a connector provided with line-relays 75 and 78, said line-relay 7 5 provided with'a couple of windings 7G and 77 said relay 78 provided withA a couple ot windings 79 and 80. ai circuit including' said windings 7G and 79 in series, a battery `B permanently connected in said circuit, a trunk release spring 'connected ini said circuit, al coperating trunk release spring 21st,y a local energizing circuit including said relays 75 and 7S and controlled by said trunk release springs, a trunk release conductor 1111 included in said local ener(fi/inty IJ J circuit, a ground terminal a't the end of said trunk release condii'ctor, said relays 75 and 78' energized until the said ground connection is broken, the said local energizing circuit being independent of th@ control of the' connector', linec'onductors 1&9' and'` 140, dings 77 andV S0 being nornially the' i bridged in series across the said line-conductors and `nmfmally connected to' the battery B at a point between them, and' means for grounding the line-conductors 139 and las@Z to energize' the relaysy 75 and 7 S, for the purpose set" forth.

In a telephone exchange system", the cc'nibinatic et :i connector provided with a releaserelay, -means for normally shortcircuiting said relay, a backfbridge-reiay the said release-circuit closed and the re'-VV lease magnet and back-release relay eric?- gized when said springs are separated.

7. In a telephone exchange system, the combination ot' a closed circuit comprising a releasemagnet and a trunk release conducto'r,v trunk release springs, together with release-relay springs, said circuit provided with a normally open switch-point between the trunk release springs, and with a normally closed switch-point at the said relay springs, said circuit closed by closure or' connection between the trunk-release springs, and the release-relay springs, as set forth.

8. In a telephone exchange system, the combination of a connector provided with a busy lock-ont relay having an' energizing circuit, 'switch-shaft springs normally controlling said "circuit, ringer-relay springs normally controlling said circuit, anda rota'ry-line-relay normally controlling said cir"- cuit.

ringer-relay, means including a back-bridgerelfliy tor short-circuiting said ringer-relay,

connections for extending the short-circuit f through ground, the short-circnit through ground closed when the springs of said relay are close'dtogether. f

`10. In a telephone exchange system, the combination of a coi'inector pioyided with anl ringer-relay. aV private-wiper, a grounded private-bank contact, means for ei'iergiiiiig said rii'iger-relay its soon' as the said wiper strikes the said grounded private-'bank 4con-Y tact, a side-switch,A an energizingy circuit for' said relay, a side-switehlwiper, and hackbridge-relay sl'jri-ngs; and an energi'ing' cir`' cuit including the' grounded privtte-banl? contact, the said private-wiper, the said side'- switch-wipcr and said loack-ln'idgelr'elay' springs.

11. In a telephone exchange systeni, the con'ibination of a connector.' proiided w .h a

busy loclr-out relay, a private-magnet, a line'- relay, ai rutger-relay, a private-wiper, a side- 'i switch, it busy line, means for energizing the ringer-relay when the private-wiper linds the busy line, and means vtor simultaU neously energizing the lock-out relay and said private magnet when the rotary-line relay is energized after the energizing oil the ringer-relay.

12. In a telephone exchange system, the combination et' a connector pro\f' idet,l with a busy lock-out relay, an energizing circuit for said relay, controlled by the relay itselt, a switch-shaft, springs operated by the sha tt, and means for retaining the relay energized until the springs are opened by the switchshaft.

13. In a telephone exchange system, the combination of a connector provided with a private-magnet having a plurality ot' energizing circuits, a line-relay controlling one of said circuits, private springs, and a busy loclcout relay controlling another of said circuits, a switch-shaft, springs operated by thc shaft, and means :tor simultaneously energizing the private magnet and the loclcout relay until the switch-shaft separates the springs operated thereby.

1l-. In a telephone exchange system, a side switchlcss selector provided with a line-relay. ground-spring, release-armature springs, and a private magnet spring normally connccted to ground through said release-arn1a ture springs.

15. In a telephone system, automatic switches, a three-wire trunk connecting said switches, a release circuit including the third conductor of the trunk, one oit said switches provided with a pair ot line relays having windings included in said release circuit, and means for sunnlving talking current over the other two wires ot' said trunk to thc station oli the calling subscriber.

16. In a telephone system, a tr1|11ksclector, a three-wire trunk leading vfrom said selector, an automatic switch allotted to the other end of said trunk, a line relay 'tor said automatic switch, a trunk-release circuit i11- cluding a winding ol said line relay in series with the third wire ot said trunk, and means for supplying talking current over the other two wires ot said truuk to the station otl the calling subscriber.

17. In a telephone system, an automatic trunk selector, a threewire trunk leading from said selector, a connector allotted to the other end of said trunk, a called telephone line temporarily seized by said con-- nector, line relays for said connector, a trunk-release circuit including a winding ol said line relays in .series with the third wire o1 said trunk, and means 'for supplying talking current over the other two wires o'l' said trunk to the station of the calling subscriber.

18. In a telephone system. automatic switches including an automatic trunk selector, line relays for said automatic switches, a trunk-release circuit for said selector, and a trunk conductor and a line re lay winding o'l" another automatic switch included in said circuit and excluded from the talking circuit.

1t). In a telephone exchange system, the combination ol a calling telephone line, a called telephone line, automatic switching machinery 'tor connectlng the two lines together, said machinery comprising banks of line terminals, line wipers adapted to cooperate with said terminals in making connections, said terminals arranged in rows, means Vfor moving the wipers in one dircction while out ol contact with said tern1inals, means 'tor moving the said wipers in another direction while in contact with the terminals of a selected row, and means tor opening the circuit of either telephone line to release the switching machinery.

Q0. In a telephone exchange system, a progressively movable automatic switch, an oll'- normal signal, a circ-uit lor said signal, a shal'l, a cam 011 said shaft, springs directly controlled by said shaft and springs controlled through the medium o1 said cam, said springs contained in the said circuit whereby the said signal is controlled by the shaft both directly and through the cam.

21. In a telephone system, two lines connectcd through the medium ol trunking apparatus and a common battery connector switch, a double wound line relay associated with said connecting circuit, release means Ain said connector controlled through the medimn ot said line relay by opening either line imlepemlent ot the other line.

22. In a telephone system, two lines connectcd through the medium ol trunking` apparatus and a connnon battery connector switch, a double wound line relay associated with said connecting circuit, release means in said connector controlled Vlrom either line through the medium ot said line relay when either line is opened` said lines being separated during the connection by a condenser on each side, said line relay being connected with the line on one side ot the comlensers.

Q3. In a telephone system, an automatic switching apparatus 'lor connecting one talking circuit with another, a release circuitl associated with said talking circuit and separate therefrom, said switching apparatus provided with line relays having windings in the release circuit and windings connected to the talking circuit,

121i. In a telephone system, an automatic switching apparatus for connecting one talking circuit with another, a release circuit associated with said talking circuit, said switching apparatus provided with line relays having windings in the release circuit and windings connected to the talkin cuit, the windings in the release circuit bemg 1n series.

In a telephone system, an automatic cirwindings in the release eirehit being in 1 series.

Signed by ine at Chicago, Cook county, illinois, this 80th day of April7 1906.

HERBERT L. FISH.

switching apparatus for Connecting one talk ing Circuit with another, a release Circuit associated with said talking Circuit, said switching apparatus provided' with line re-` lays having windings in the release Circuit and windings connected to the talking eir- Cuit, said automatic switching apparatus comprising a connector switch and said line relays being located in said connector, the

Witnesses:

EDWARD D. FALEs', R. H. BURFEIND.

Copies of this patent may be obtained.l for ve eents each, by addressing `the Commissioner of Patents,

Washington, D. C. 

